Method and system for heating solid tissue

Abstract

Methods for heating tissue by delivering radio frequency energy through tissue electrodes comprise controlling energy delivery so that an abrupt increase in impedance between the electrodes and the tissue is observed, typically in the form of an abrupt decrease in power delivered to the electrodes. The power at which the impedance increases and/or the time required to induce such an increase in impedance, are relied on to determine acceptable ranges to achieve a maximum sustainable delivery of radio frequency energy to the tissue consistent with complete, rapid, and uniform heating of the tissue.

What is claimed is:  
     
       1. A method for heating a treatment region within solid tissue, comprising: 
       introducing an electrode within the treatment region; and  
       energizing the electrode by delivering power to the electrode using a programmable power supply, wherein the power supply is programmed to  
       increase power being delivered to the electrode to an elevated power level at which a rapid increase in electrode-tissue interface impedance occurs,  
       reduce power sufficiently below the elevated level to permit the electrode-tissue interface impedance to decrease, and  
       reenergize the electrode by delivering power to the electrode at a level below the elevated level.  
     
     
       2. The method of  claim 1 , wherein the elevated power level is in the range from 50 W to 200 W. 
     
     
       3. The method of  claim 1 , wherein the power supply is programmed to increase the power to the elevated level linearly at a rate in the range from 10 W/minute to 15 W/minute. 
     
     
       4. The method of  claim 1 , wherein the power supply is programmed to increase the power to the elevated level non-linearly at a rate which increases within the range from 5 W/minute to 25 W/minute. 
     
     
       5. The method of  claim 1 , wherein the power supply is programmed to initially energize the electrode at a level that is 50% to 90% of the elevated power level. 
     
     
       6. The method of  claim 1 , wherein the power supply is further programmed to cease increasing the delivered power level when a decrease in a delivered power to the electrode is detected. 
     
     
       7. The method of  claim 6 , wherein the power supply is further programmed to measure a time elapsed from the delivered power is first increased to when the rapid increase in electrode-tissue interface impedance occurs. 
     
     
       8. A computer readable medium having stored instructions, the execution of which causes a process to be performed, the process comprising: 
       energizing a tissue-contacting electrode by delivering power to the electrode;  
       increasing power being delivered to the electrode to an elevated power level at which a rapid increase in electrode-tissue interface impedance occurs;  
       reducing power sufficiently below the elevated level to permit the electrode-tissue interface impedance to decrease; and  
       reenergizing the electrode by delivering power to the electrode at a level below the elevated level.  
     
     
       9. The method of  claim 8 , wherein the level at which the power is delivered to the electrode is determined based at least in part on the measured time. 
     
     
       10. The computer readable medium of  claim 8 , wherein the elevated power level is in the range from 50 W to 200 W. 
     
     
       11. The computer readable medium of  claim 8 , the process further comprising increasing the power to the elevated level linearly at a rate in the range from 10 W/minute to 15 W/minute. 
     
     
       12. The computer readable medium of  claim 8 , the process further comprising increasing the power to the elevated level non-linearly at a rate which increases within the range from 5 W/minute to 25 W/minute. 
     
     
       13. The computer readable medium of  claim 8 , wherein the electrode is initially energized at a level that is 50% to 90% of the elevated power level. 
     
     
       14. The computer readable medium of  claim 8 , the process further comprising measuring a time elapsed from the delivered power is first increased to when the rapid increase in electrode-tissue interface impedance occurs. 
     
     
       15. The computer readable medium of  claim 14 , wherein the level at which the power is delivered to the electrode is determined based at least in part on the measured time. 
     
     
       16. The computer readable medium of  claim 8 , the process further comprising ceasing increasing the delivered power level when a decrease in a delivered power to the electrode is detected. 
     
     
       17. A system for energizing an electrode disposed within a solid tissue region, comprising: 
       means for energizing the electrode by delivering power to the electrode using a programmable power supply, wherein the power supply is programmed to  
       increasing power being delivered to the electrode to an elevated power level at which a rapid increase in electrode-tissue interface impedance occurs,  
       reducing power sufficiently below the elevated level to permit the electrode-tissue interface impedance to decrease, and  
       reenergizing the electrode by delivering power to the electrode at a level below the elevated level.  
     
     
       18. The system of  claim 17 , further comprising means for measuring a time elapsed from when the power being delivered to the electrode is increased to when the rapid increase in electrode-tissue interface impedance occurs.